High-Temperature Transformation Of Vicinal (0001) Al2o3-Alpha Surfaces: An Afm Study

Development of the morphology of vicinal (0001) surfaces of alpha-alumina, induced by annealing in air at 1500 degrees C, was studied by AFM. Our investigation shows that the resulting surface morphology depends on both the duration of thermal treatment and the surface misorientation relative to crystallographic directions, The whole vicinal surface, which is initially covered by steps of 0.21 nm height, after heating can exhibit tno kinds of morphologies due to step bunching or step faceting, Step bunching occurs even after a relatively short annealing time (1 h) and is found to depend on the miscut angle. Further annealing of bunched stepped surfaces leads to the disappearance of bunching, leaving sometimes a new faceted phase. In the general case of facets, the border of faceted steps follows the [10 (1) over bar 0] crystallographic direction, and less closely the [10 (2) over bar 0] direction, producing zigzags. The faceting process is triggered by the step height exceeding a certain value, The origin of incubation time for the faceting process is discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.